The sea is one of the largest unexploited sources of renewable energy on the planet: ENEA and RSE have calculated that if the energy produced by oceans (waves, tides, salinity and thermal gradient) could be fully harnessed, we could obtain as many as 80,000 TWh of energy, around five times the entire world’s annual electricity demand. Other estimates put this figure as high as 130,000 TWh. According to the most conservative estimates, the wave component alone is thought to be about 2 TW globally, equivalent to about 18,000 TWh per year, or almost the entire planet's annual electricity demand. Our ISWEC (Inertial Sea Wave Energy Converter) system does exactly that: it converts the energy of ocean waves into electrical energy, making it immediately available for offshore plants or feeding it directly into the electricity grid to provide power to coastal communities and small islands. ISWEC was developed together with Wave for Energy S.r.l., a spin-off of the Politecnico di Torino. The system consists of a sealed floating hull containing a pair of gyroscopic systems connected to two generators. Gyroscopes are large, constantly rotating flywheels that tend to keep their rotational axis fixed by generating a force perpendicular to the axis in order to counter external forces that tend to change it. The phenomenon is known as gyroscopic precession. The waves cause the unit to pitch; it is anchored to the ocean floor, but it is free to move and oscillate. The hull's pitching movement is intercepted by the two gyroscopic systems: they are connected to just as many generators that produce electric energy. It is a simple solution, with cutting-edge technology at its heart.
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ISWEC from pilot plant to Pantelleria
ISWEC is perfect for supplying electricity to off-grid smaller islands, coastal communities e offshore plants, and to Oil & Gas platforms in particular. The first pilot plant was installed in Ravenna in March 2019, connected to our PC80 platform and integrated with a photovoltaic plant. The plant was then decommissioned in September 2022. This type of application increases the energy self-sufficiency of offshore facilities that are located away from the coast, perhaps in geographical contexts where electricity supply cannot be taken for granted.
In February 2023, Eni completed the installation of the first ISWEC device in the Mediterranean sea, 800 metres off the coast of Pantelleria.
Facts and figures of ISWEC in Pantelleria
The ISWEC model installed off the coast of Pantelleria consists of a steel hull, measuring 8x15m which houses the energy conversion system, consisting of two gyroscopic units of more than 2m in diameter each. The device is held in place on a 35-metre-deep seabed by a mooring that aligns with weather and sea conditions, consisting of three chains connected to a pivot pin, while the electricity produced is brought ashore through an underwater power cable. The device will be capable of reaching 260 kW peak energy production from wave motion and it will also be used to acquire data to optimise the design of new devices.
Besides waves, there are many other ways the sea can provide clean energy. To study and make the most of the potential of seas and oceans, in collaboration with the Politecnico di Torino we have created MORE – Marine Offshore Renewable Energy Lab, a laboratory entirely dedicated to developing technologies to harness not just wave energy, but also that of ocean currents, tides and the salt gradient, as well as to improve offshore wind and solar energy production.
Our commitment to the development of the renewable marine energy sector has been further strengthened by our joining as lead partner Ocean Energy Europe (OEE), the largest European network for the development of ocean energy. This position allows us to collaborate to chart the strategic course of projects aimed at developing and marketing offshore marine technological solutions to produce renewable energy.
The technological challenge
Wave energy is the most constant of all renewable energy types: unlike the sun and the wind, the sea never stays still. It is also the most “dense”, as it concentrates the energy produced by the wind and that produced by the heating of the atmosphere by the sun.
There were two main issues associated with ISWEC to be resolved: corrosion due to salt in the water and the optimization of device operation as the intensity of the waves varies. We succeeded in resolving both of these because the moving parts, which are the most delicate, are inside the sealed hull and they are completely isolated from the sea environment, while the functioning of the gyroscopic systems that feed the two generators is optimised by a system that responds to varying weather and sea conditions. ISWEC has an active component in the energy capture process, which is regulated by the flywheel’s rotation speed and by the torque of the generator and and lets the hull’s inertia adapt to the marine wavelength that affects it; this feature, which was implemented for the first time in the world by Eni on an prototype, is what significantly differentiates it from other capture systems: it is possible to vary the device’s inertia just as if we were changing its size, thereby obtaining a virtual variable geometry system.
A new development
ISWEC is an example of the teamwork that lies behind all of our proprietary technology. In this instance, one of the most delicate technological challenges to be overcome was the sizing of the gyroscopic system in order to optimise its response to local sea conditions, which was a fundamental step in taking full advantage of the constant availability that is the most significant feature of wave energy. The task was to analyse and cross-reference large amounts of data from different sources, both weather data and information relating to the operation of the machine. HPC4 and HPC5, our supercomputers, provided the assistance we needed: thanks to their computing power, we use advanced mathematical models to develop answers suited to every weather and sea situation. A further technological addition to ISWEC was the installation of photovoltaic panels on the deck of the hull, which provide a large surface area for capturing sunlight. Furthermore, the integration between our people and facilities and the MORE Lab is particularly deep and many-faceted. The laboratory is based at the Politecnico and uses the Department of Mechanical and Aerospace Engineering’s research infrastructure combined with the Marine Virtual Lab at the Green Data Center in Ferrera Erbognone, which uses the HPC5 supercomputer.
The MORE Lab forms a network with our site in Pantelleria, where ISWEC is connected to the island's power grid. ISWEC contributes to the island's energy autonomy and to eliminating any impact potentially caused on the landscape by industrial facilities on the island. At full capacity, the MORE Lab employs about 50 researchers who work together with our people to quickly get more specific knowledge and finalise technologies for industrial use. The centre also has a naval test tank and state-of-the-art laboratories. The Politecnico di Torino simultaneously set up a special chair in “Sea Energy” so engineers can be trained to specialise in the design, implementation and use of new technologies that will be developed at the laboratory.
ISWEC – The energy that comes from the sea | Eni Video Channel
Electricity from sea waves
ISWEC's nominal power when connected to the Pantelleria electricity grid
peak power of energy extraction from sea waves that can be generated by ISWEC in Pantelleria
average wave power density in Pantelleria
global sea wave energy potential
Impact on the environment
Although different from one another in many ways, all coastal towns and villages share similar characteristics, as they have similar needs. A small inhabited island is not so different from an oil rig. For this reason, it is possible to supply electricity from renewable sources to communities living on small islands. Moreover, ISWEC can be integrated perfectly with other offshore renewable energy production systems, such as wind power generators, both to enhance electrical grid connection systems and because it can be integrated within the same sea area, thereby maximising the conversion of the available energy. A further advantage of this technology is the considerable reduction of its impact on the landscape , since the device stands only 1 metre above sea water.
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